Cotton (Gossypium hirsutum L.) belonging to family Malvaceae and genus Gossypium. Cotton can be grown between latitudes 30°N to 30°S, While, yield and fibre quality are considerably influenced by climatic conditions, higher moisture levels resulting from rainfall or irrigation during growing season and a dry, warm conditions during picking results in production of superior quality cotton. Optimum sowing time is considered as the most crucial non monetary input and important manageable factor which have favourable effect on crop growth and yield. Crops that are planted too early have poor crop stand, which reduces yield potential while delayed sowing causes the crop to not reach maximum canopy production, making it more susceptible to lower temperature stress at later stages of crop growth, leading to poor growth and yield. Temperature, rainfall, relative humidity and radiation are the important meteorological parameters that affects the crop at different phenophases and finally alter the crop production. Cotton requires daily minimum temperature of 16°C for seed germination, 21-27°C for better vegetative growth. It can tolerate temperatures as high as 43°C. During fruiting phase temperature ranging from 27 to 32°C is optimum for crop. Higher yields and yield attributes are observed in early sown (30^th April) crop at wider spacing (67.5cm × 75 cm) and E-Wrow orientation. Increase in both maximum and minimum temperature decreases the yield of the crop and decrease in amount of rainfall also decreases the yield of the crop. The most critical growth period deciding the cotton seed yield is from square formation to boll bursting. Yield attributes and yield were significantly higher under irrigated cotton as compared to rainfed cotton. The TUE (Thermal use efficiency) was found maximum in the cotton planted under wider plant spacing 67.5 × 75 cmat all the phenophases and seed cotton yield is also maximum at this spacing. 15th April to 1st May is the optimum period for cotton planting in Pakistan, early/delayed planting results in reduction of seed cotton yield as the crop completes its life cycle in short duration and accumulates lesser GDD (Growing degree days).

Meteorological Parameters, Rainfed, TUE, GDD